Surgical cannulas and surgical trocars are well known in the art.
Surgical cannulas are essentially tube-like members which are inserted into openings made in the body so as to line the openings and maintain them against closure. Surgical cannulas are used during so-called "closed" surgical procedures (e.g. laparoscopic procedures) to provide a portal between the region outside the body and the interior surgical site. In essence, the surgical cannulas serve as protective liners to allow surgical instruments to be inserted into, and withdrawn from, the internal surgical site with a minimum of trauma to the intervening tissue.
Surgical trocars are sharp, pointed instruments which are used to make openings in tissue so as to facilitate proper placement of the surgical cannulas in the body. More particularly, a surgical trocar is typically inserted into a cannula so that the trocar's sharp distal tip protrudes from the distal end of the cannula. The cannula and trocar are then advanced through the tissue as a unit, with the trocar's sharp tip leading the cannula so as to open up the tissue before the advancing cannula. Once the cannula has penetrated the tissue to the extent required, the trocar is withdrawn from the cannula. The cannula may thereafter be used to pass surgical instruments to and from the interior surgical site.
As noted above, when the trocar has been inserted into the cannula, the sharp distal tip of the trocar extends out of the distal end of the cannula. It will be appreciated, therefore, that this arrangement causes serious concerns among operating room personnel, since the sharp tip of the trocar is exposed and could cause injury to anyone accidentally coming into contact with the tip. This concern is heightened inasmuch as AIDS, hepatitis and/or other life-threatening disorders could be transferred from one person to another through such an injury. Thus, it is desirable to provide some sort of shield arrangement to protect operating room personnel from accidental contact with trocar's sharp point.
One such arrangement has been developed by United States Surgical Corp. ("USSC") of Norwalk, Conn. More particularly, USSC currently markets a surgical cannula and trocar system under the trade names "Auto Suture" and "SURGIPORT" wherein the trocar is provided with a telescoping sheath member which is capable of alternatively covering or exposing the trocar's sharp tip. Various locking arrangements are provided on the trocar which coact with counterpart elements on the surgical cannula to control sheath movement relative to the trocar's sharp tip.
Unfortunately, the foregoing surgical cannula and trocar system of USSC suffers from a number of disadvantages. Among other things, it requires that the surgical trocar be more complex in design. This increased complexity is undesirable, inasmuch as it leads to greater cost of manufacture and increased possibility of malfunction.
Furthermore, in laparoscopic procedures of the sort commonly used today, a plurality of surgical cannulas are typically inserted through the abdominal wall so that their distal ends reside inside the abdominal cavity while their proximal ends reside outside the body. In addition, in order to improve visual and instrument access to the interior surgical site, the patient's abdomen is typically inflated with a pressurized gas so as to extend the abdominal wall away from the interior organs. Inasmuch as the cannulas serve as a conduit between the pressurized surgical cavity and the region outside the body, some sort of sealing means must generally be provided with the surgical cannulas to prevent the pressurized gas from escaping out through the cannula, since this could cause the abdomen to deflate during the surgical procedure.
In this regard it should also be appreciated that the aforementioned sealing means must be effective both when an instrument extends through the cannula as well as when no instrument extends through the cannula. Furthermore, the sealing means must be capable of maintaining a good seal about an instrument even as the instrument is moved about during a surgical procedure. Unfortunately, the various sealing means heretofore provided on surgical cannulas have proven somewhat less than satisfactory, for a variety of different reasons.